| 1. |
- Brohede, Samuel, 1977, et al.
(författare)
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Internal consistency in the Odin stratospheric ozone products
- 2007
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Ingår i: Canadian Journal of Physics. - 0008-4204 .- 1208-6045. ; 85:11, s. 1275-1285
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Tidskriftsartikel (refereegranskat)abstract
- The two independent instruments on the Odin satellite, the Optical Spectrograph and Infrared Imaging System (OSIRIS) and the Sub-Millimetre Radiometer (SMR) produce atmospheric profiles of various atmospheric species including stratospheric ozone. Comparisons are made between OSIRIS version 3.0 and SMR version 2.1 ozone data to evaluate the consistency of the Odin ozone data sets. Results show good agreement between OSIRIS and SMR in the range 25–40 km, where systematic differences are less than 15% for all latitudes and seasons. Larger systematic differences are seen below 25 km, which can be explained by the increase of various error sources and lower signals. The random differences are between 20–30% in the middle stratosphere. Differences between Odin up-scans and down-scans or AM and PM are insignificant in the middle stratosphere. Furthermore, there is little variation from year to year, but a slight positive trend in the differences (OSIRIS minus SMR) of 0.045 ppmv/year at 30 km over validation period (2002–2006). The fact that the two fundamentally different measurement techniques, (absorption spectroscopy of scattering sunlight and emission measurements in the sub-millimetre region) agree so well, provides confidence in the robustness of both techniques.
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| 2. |
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| 3. |
- Jones, Ashley, 1977, et al.
(författare)
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Analyzing the applications of an assimilation model as a method for validation of satellite data
- 2007
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Ingår i: Journal of Geophysical Research. - 0148-0227 .- 2156-2202. ; 112:D17101
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Tidskriftsartikel (refereegranskat)abstract
- An analysis was performed to illustrate that data assimilation is an appropriate method for validation of satellite measurements when very few coincidences are available between satellite measurements and balloon sondes. Results showed that the mean differences between the Isentropic Assimilation model for StratospheriC Ozone (IASCO) model ozone profiles and co-located ozone sondes shared systematic differences similar to those obtained from co-located MIPAS and ozone sonde coincidences. The spatial and temporal constraints of 12 hours and 800 km produced the optimal number of MIPAS/sonde matches for a statistical analysis. The largest residual between the IASCO/sonde mean difference and MIPAS/sonde mean difference, using these constraints, was less than 0.25 ppmv, between potential temperature levels of 425-975 K. By using the assimilation model coincidences, we also conclude that the maximum time/distance constraint sizes that can be used when obtaining matches between satellite measurements and in-situ measurements should be no more than 24 hours and a maximum of 1500-2000 km. However, local conditions such as the presence of a dynamical feature, for example the edge of the polar vortex, may of course greatly restrict these limits.
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| 4. |
- Jones, Ashley, 1977, et al.
(författare)
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Evolution of stratospheric ozone and water vapour time series studied with satellite measurements
- 2009
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Ingår i: Atmospheric Chemistry and Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 9, s. 6055-6075
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Tidskriftsartikel (refereegranskat)abstract
- The long term evolution of stratospheric ozone and water vapour has been investigated by extending satellite time series to April 2008. For ozone, we examine monthly average ozone values from various satellite data sets for nine latitude and altitude bins covering 60° S to 60° N and 20–45 km and covering the time period of 1979–2008. Data are from the Stratospheric Aerosol and Gas Experiment (SAGE I+II), the HALogen Occultation Experiment (HALOE), the Solar BackscatterUltraViolet-2 (SBUV/2) instrument, the Sub-Millimetre Radiometer (SMR), the Optical Spectrograph InfraRed Imager System (OSIRIS), and the SCanning Imaging Absorption spectroMeter for Atmospheric CHartograpY (SCIAMACHY). Monthly ozone anomalies are calculated by utilising a linear regression model, which also models the solar, quasi-biennial oscillation (QBO), and seasonal cycle contributions. Individual instrument ozone anomalies are combined producing an all instrument average. Assuming a turning point of 1997 and that the all instrument average is represented by good instrumental long term stability, the largest statistically significant ozone declines (at two sigma) from 1979–1997 are seen at the mid-latitudes between 35 and 45 km, namely −7.2%±0.9%/decade in the Northern Hemisphere and −7.1%±0.9%/in the Southern Hemisphere. Furthermore, for the period 1997 to 2008 we find that the same locations show the largest ozone recovery (+1.4% and +0.8%/decade respectively) compared to other global regions, although the estimated trend model errors indicate that the trend estimates are not significantly different from a zero trend at the 2 sigma level. An all instrument average is also constructed from water vapour anomalies during 1991–2008, using the SAGE II, HALOE, SMR, and the Microwave Limb Sounder (Aura/MLS) measurements. We report that the decrease in water vapour values after 2001 slows down around 2004–2005 in the lower tropical stratosphere (20–25 km) and has even shown signs of increasing until present. We show that a similar correlation is also seen with the temperature measured at 100 hPa during this same period.
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| 5. |
- Jones, Ashley, 1977, et al.
(författare)
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Intercomparison of Odin/SMR Ozone measurements with MIPAS and balloon sonde data
- 2007
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Ingår i: Canadian Journal of Physics. ; 85:11, s. 1111-1123
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Tidskriftsartikel (refereegranskat)abstract
- The Sub-Millimetre Radiometer (SMR) on board Odin measures various important atmospheric species, including stratospheric ozone. In this study we compare the three versions (v1.2, v2.0 and v2.1) of level 2 Odin/SMR global stratospheric ozone data to coincident level 2 MIPAS V4.61 and balloon sonde stratospheric ozone data during 2003. The most current product from Odin/SMR (at time of writing), the v2.1, showed the smallest systematic differences when compared to coincident MIPAS and sonde data. Between 17 and 55 km, v2.1 values agreed with MIPAS within 10% (a maximum of 0.42 ppmv), while comparisons to sonde measurements showed an agreement of typically 5-10% between 22 and 35 km (less than 0.5 ppmv below 33 km). Tropical latitudes below 35 km preseneted the largest absolute systematic differences between v2.1 and sonde coincidences, where Odin/SMR was systematically lower by ~0.9 ppmv (more than 10% difference) at approximately 30 km. Comparisons concerning the previous two Odin/SMR versions showed much larger systematic differences, especially at the higher and lower stratospheric altitudes. The main conclusion here is that we suggest that v2.1 of Odin/SMR ozone data should be used for scientific studies.
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| 6. |
- RÖSEVALL, JOHN, 1977, et al.
(författare)
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A study of polar ozone depletion based on sequential assimilation of satellite data from the ENVISAT/MIPAS and Odin/SMR instruments
- 2007
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Ingår i: Atmospheric Chemistry and Physics. - 1680-7316 .- 1680-7324. ; 7:3, s. 899-911
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Tidskriftsartikel (refereegranskat)abstract
- The objective of this study is to demonstrate how polar ozone depletion can be mapped and quantified by assimilating ozone data from satellites into the wind driven transport model DIAMOND, (Dynamical Isentropic Assimilation Model for OdiN Data). By assimilating a large set of satellite data into a transport model, ozone fields can be built up that are less noisy than the individual satellite ozone profiles. The transported fields can subsequently be compared to later sets of incoming satellite data so that the rates and geographical distribution of ozone depletion can be determined. By tracing the amounts of solar irradiation received by different air parcels in a transport model it is furthermore possible to study the photolytic reactions that destroy ozone. In this study, destruction of ozone that took place in the Antarctic winter of 2003 and in the Arctic winter of 2002/2003 have been examined by assimilating ozone data from the ENVISAT/MIPAS and Odin/SMR satellite-instruments. Large scale depletion of ozone was observed in the Antarctic polar vortex of 2003 when sunlight returned after the polar night. By mid October ENVISAT/MIPAS data indicate vortex ozone depletion in the ranges 80–100% and 70–90% on the 425 and 475 K potential temperature levels respectively while the Odin/SMR data indicates depletion in the ranges 70–90% and 50–70%. The discrepancy between the two instruments has been attributed to systematic errors in the Odin/SMR data. Assimilated fields of ENVISAT/MIPAS data indicate ozone depletion in the range 10–20% on the 475 K potential temperature level, (~19 km altitude), in the central regions of the 2002/2003 Arctic polar vortex. Assimilated fields of Odin/SMR data on the other hand indicate ozone depletion in the range 20–30%.
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| 7. |
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| 8. |
- Barret, B., et al.
(författare)
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Intercomparisons of trace gases profiles from the Odin/SMR and Aura/MLS limb sounders
- 2006
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Ingår i: Journal of Geophysical Research. - 0148-0227 .- 2156-2202. ; 111:D21
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents the intercomparison of O(3), HNO(3), ClO, N(2)O and CO profiles measured by the two spaceborne microwave instruments MLS ( Microwave Limb Sounder) and SMR ( Submillimetre Radiometer) on board the Aura and Odin satellites, respectively. We compared version 1.5 level 2 data from MLS with level 2 data produced by the French data processor version 222 and 225 and by the Swedish data processor version 2.0 for several days in September 2004 and in March 2005. For the five gases studied, an overall good agreement is found between both instruments. Most of the observed discrepancies between SMR and MLS are consistent with results from other intercomparison studies involving MLS or SMR. O(3) profiles retrieved from the SMR 501.8 GHz band are noisier than MLS profiles but mean biases between both instruments do not exceed 10%. SMR HNO(3) profiles are biased low relative to MLS's by similar to 30% above the profile peak. In the lower stratosphere, MLS ClO profiles are biased low by up to 0.3 ppbv relative to coincident SMR profiles, except in the Southern Hemisphere polar vortex in the presence of chlorine activation. N(2)O profiles from both instruments are in very good agreement with mean biases not exceeding 15%. Finally, the intercomparison between SMR and MLS CO profiles has shown a good agreement from the middle stratosphere to the middle mesosphere in spite of strong oscillations in the MLS profiles. In the upper mesosphere, MLS CO concentrations are biased high relative to SMR while negative values in the MLS retrievals are responsible for a negative bias in the tropics around 30 hPa.
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| 9. |
- Jones, Ashley, 1977, et al.
(författare)
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Analysis of HCl and ClO time series in the upper stratosphere using satellite data sets
- 2011
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Ingår i: Atmospheric Chemistry and Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 11:11, s. 5321-5333
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Tidskriftsartikel (refereegranskat)abstract
- Previous analyses of satellite and ground-based measurements of hydrogen chloride (HCl) and chlorine monoxide (ClO) have suggested that total inorganic chlorine in the upper stratosphere is on the decline. We create HCl and ClO time series using satellite data sets extended to November 2008, so that an update can be made on the long term evolution of these two species. We use the HALogen Occultation Experiment (HALOE) and the Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE-FTS) data for the HCl analysis, and the Odin Sub-Millimetre Radiometer (SMR) and the Aura Microwave Limb Sounder (Aura-MLS) measurements for the study of ClO. Altitudes between 35 and 45 km and two mid-latitude bands: 30° S–50° S and 30° N–50° N, for HCl, and 20° S–20° N for ClO and HCl are studied. ACE-FTS and HALOE HCl anomaly time series (with QBO and seasonal contributions removed) are combined to produce all instrument average time series, which show HCl to be reducing from peak 1997 values at a linear estimated rate of −5.1 % decade−1 in the Northern Hemisphere and −5.2 % decade−1 in the Southern Hemisphere, while the tropics show a linear trend of −5.8 % per decade (although we do not remove the QBO contribution there due to sparse data). Trend values are significantly different from a zero trend at the 2 sigma level. ClO is decreasing in the tropics by −7.1 % ± 7.8 % decade−1 based on measurements made from December 2001 to November 2008. The statistically significant downward trend found in HCl after 1997 and the apparent downward ClO trend since 2001 (although not statistically significant) confirm how effective the 1987 Montreal protocol objectives and its amendments have been in reducing the total amount of inorganic chlorine.
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| 10. |
- Jones, Ashley, 1977
(författare)
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Techniques for the validation of Odin and ENVISAT satellite data
- 2007
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The depletion of ozone from the stratosphere and the impact of global warming have been identified as phenomena caused as a result of anthropogenic activity. Scientists are thus trying to find quicker and more reliable ways to analyse these environmental problems. Remote sensing of the atmosphere using satellites is perhaps the most cost effective method. One beneficial application is the acquisition of vertical profiles of atmospheric species on a global scale with good spatial and temporal resolutions. An example of an instrument that can achieve this is the Sub-Millimetre Radiometer (SMR) aboard the Odin satellite that launched in 2001, which retrieves vertical limb profiles of numerous trace gases, including stratospheric ozone.This thesis presents a validation for Odin/SMR ozone data products, V1.2, V2.0 and V2.1 (for the 501.8 GHz band in the microwave region). Comparisons were made to V4.61 data from the Interferometer for Passive Atmospheric Soundings (MIPAS) instrument, on board the ENVISAT satellite. Further analysis was carried out by comparing Odin/SMR mixing ratios to balloon sonde data. By validating these three versions of Odin/SMR data, we can establish if any further adjustments need be made to the settings and calibrations of the instruments for the production of subsequent data sets. Such an investigation can be achieved either by matching coincident data using time and distance constraints directly or by using a data assimilation modelThe latest and current version, V2.1, of Odin/SMR showed comparisons with MIPAS V4.61 and balloon sonde data to have the smallest systematic differences with respect to the previous two versions, especially below 25 km. In this lower stratospheric region, V2.1 was only slightly smaller than MIPAS by less than 0.25 ppmv, while comparisons to sonde measurements showed an agreement within +/-0.3 ppmv. The largest systematic differences for this version were seen in the tropics, where a bias of ~0.7 ppmv between 25-37 km was found. An analysis was done in order to prove that data assimilation is a valid method for validation of satellite measurements when very few coincident data are available between satellite measurements and balloon sondes. Results showed that mean differences between the Isentropic Assimilation model For Stratospheric Ozone (IASCO) produced ozone profiles and co-located ozone sondes contained systematic differences similar to those obtained from co-located MIPAS and ozone sonde coincidences. Spatial and temporal constraints were used to obtain the MIPAS/sonde matches, where 12 hours and 800 km produced the best results for statistical analysis. The largest residual between the IASCO/sonde mean difference and MIPAS/sonde mean difference using these constraints was less than 0.25 ppmv between potential temperature altitudes of 425-975 K
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